Interpretive Summary: An important by-product of cassava starch extraction is the fiberous pulp residue that contains about 50% starch and is an underutilized and often wasted resource. Researchers at Embrapa in Brazil and scientists at the Western Regional Research Center in Albany, CA showed that the cassava by-product could be processed into thermoplastic starch with improved strength. It was also useful in making poly(lactic acid) composites with good mechanical strength. The findings could help develop a new market for cassava, help rural economies, and help develop affordable, renewable composite materials and decrease our dependence on petroleum products.

Technical Abstract: Cassava bagasse is an inexpensive and broadly available waste byproduct from cassava starch production. It contains roughly 50% cassava starch along with mostly fiber and could be a valuable feedstock for various bioproducts. Cassava bagasse and cassava starch were used in this study to make fiber-reinforced thermoplastic starch (TPSB and TPSI, respectively). In addition, blends of poly (lactic acid) and TPSI (20%) and TPSB (5, 10, 15, 20%) were prepared as a means of producing low cost composite materials with functional properties similar to neat PLA. The TPS and PLA blends were prepared by extrusion and their morphological, mechanical, spectral, and thermal properties were evaluated. The results showed the feasibility of obtaining thermoplastic starches from cassava bagasse. In PLA/TPSB blends, the TPSB increased the crystallinity of the PLA component compared to neat PLA. As expected, the TPS incorporation diminished the mechanical properties with respect to neat PLA. However, TPSB had greater tensile strength and modulus than TPSI. The TPSI had higher elongation to break compared to both TPSB and PLA. These properties were also reflected in blends of PLA/TPSB and PLA/TPSI. The thermal analysis indicated that although the blends were largely immiscible, there was some low level of interaction between PLA and TPS. The fiber component of TPSB appeared to have a nucleating effect favoring PLA crystallization. The fiber also acted as a reinforcement in both the TPS and PLA blends.